Sometimes I really hate Quicken
The problem started with a situation that didn't seem so bad at first - a couple of register items ended up erroneously flagged as reconciled. I'm not sure how it happened - they were well after the date of the last statement - but it seemed like it shouldn't be hard to fix. Wrong. Several wasted hours later (which included two chat support calls to Intuit), I end up restoring from a backup and re-entering months of transactions. Apparently the ability to re-reconcile a months transactions is too much to ask for. Even the trick of deleting previous reconciliation statements I've used with previous versions of Quicken doesn't seem to work in the 2005 version - that option seems to have disappeared from the UI.
Message to Intuit - if something as simple as recovering from a reconciliation error requires restoring from a backup, it's time for a little usability work.